Historically, materials used in bicycles have followed a similar pattern as in aircraft, the goal being high strength and low weight. Since the late 1930s alloy steels have been used for frame and fork tubes in higher quality machines. In the 1980s aluminum alloy frames and other components became popular due to their light weight, and most mid-range bikes are now principally aluminum alloy of some kind.[where?] More expensive bikes use carbon fibre due to its significantly lighter weight and profiling ability,